The present invention relates, in general, to hydrocarbon conversion processes. More particularly, this invention relates to a process for the selective hydroalkylation of paraffinic hydrocarbons in the presence of a catalyst comprising a metal pentafluoride selected from the group consisting of tantalum pentafluoride, niobium pentafluoride and mixtures thereof and a hydrogen halide, wherein the product thus formed contains primarily C.sub.4 -C.sub.6 isomerized paraffins.